Light emitting device packages with improved heat transfer

ABSTRACT

Packages containing one or more light emitting devices, such as light emitting diodes (LEDs), are disclosed. In one embodiment, LED package can include a thermal element having improved solder reliability to improve heat dissipation capacity of the LED package. LED package can include a molded plastic body having one or more LEDs attached to one or more electrical elements. The LEDs can be connected to an upper surface of the thermal element. The thermal element can include a bottom surface which can extend further away in distance from a body of the LED package than a bottom surface of the electrical element. This configuration can result in an improved connection between the LED package and an external circuitry source, thereby increasing heat transfer ability of the LED package.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to co-pendingU.S. patent application Ser. No. 12/825,075 filed Jun. 28, 2010, whichrelates and claims priority to and is a continuation-in-part applicationfrom these related matters: U.S. utility patent application Ser. No.12/479,318, filed Jun. 5, 2009; U.S. design patent application Ser. No.29/330,657, filed Jan. 12, 2010; U.S. design patent application Ser. No.29/353,652 filed Jan. 12, 2010; U.S. design patent application Ser. No.29/338,186 filed Jun. 5, 2009, and U.S. design patent application Ser.No. 29/360,791 filed Apr. 30, 2010, the entire contents of all of whichare hereby incorporated by reference herein.

TECHNICAL FIELD

The subject matter disclosed herein relates generally to packages forlight emitting devices. More particularly, the subject matter disclosedherein relates to light emitting device packages with improved heattransfer.

BACKGROUND

Light emitting devices, such as light emitting diodes (LEDs) forexample, are often packaged within surface mounted device (SMD)housings. These housings are often made of plastic and are referred toas plastic leaded chip carriers (PLCCs). SMD housings can typicallyfeature an LED connected to multiple metal leads. Portions of the leadsmay be molded within a plastic body, while other portions may protrudeand extend outside of the plastic body. The molded plastic body candefine a reflector for enhanced light emission and can be coated with anencapsulant containing a phosphor, such as yttrium aluminum garnet (YAG)for obtaining light having a desired wavelength spectrum. The body ofthe SMD housing can also comprise a ceramic material. The metal leads ofthe leadframe package serve to as a channel for supplying the LED withelectrical power and, at the same time, may act to draw heat away fromthe LED chip.

Heat is generated by the LED when power is applied to the LED to producelight. The portion of the leads that can extend out from the packagebody can connect to circuits external to the leadframe package, forexample those on a printed circuit board (PCB). Some of the heatgenerated by the LED may be dissipated by the plastic package body;however, it is desirable for most of the heat to be drawn away from theLED via the metal components, or other elements of high thermalconductivity. To increase the heat dissipating capacity of an LEDpackage, a heat transfer material or substrate such as a heat slug maybe introduced into the package. Standard soldering processes such aslead-free reflow are used for assembly of the LED packages to externalsources, such as PCBs. Once soldered, the heat slug can draw heat fromthe LED chip to an external source, thus increasing the heat dissipatingcapacity of the LED package. However, conventional package designsutilize designs wherein the external surface of the heat slug is flushwith an external surface of the metal leads on a side of the package inwhich the surfaces will become attached to the PCB. To be adequate, themetal leads need only establish an electrical contact with the PCB.However, adequate contact between the PCB and heat sink is moredifficult because in order to ensure adequate thermal transfer, ideallythe entire bottom surface of the heat sink needs wetted by the solder tominimize voids. Current LED package designs can result in the surface ofthe heat sink being inadequately wetted, thus inadequately soldered tothe PCB and thereby decreasing both reliability and heat dissipation ofthe LED package. If not adequately wetted, voids can exist between thebottom surface of the heat transfer material and the PCB, thus resultingin poor heat transfer as well as heat dissipation problems.

Consequently, there remains a need for improved light emitting devicepackages that overcome or alleviate shortcomings of prior art lightemitting device packages.

SUMMARY

In accordance with this disclosure, light emitting device packages areprovided with improved heat transfer. It is, therefore, an object of thepresent disclosure herein to provide light emitting device packages withboth improved solder reliability and improved heat dissipating capacityfor improving heat transfer between a backside of the LED package and aprinted circuit board (PCB) or other receiving substrate.

These and other objects of the present disclosure as can become apparentfrom the disclosure herein are achieved, at least in whole or in part,by the subject matter described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present subject matter includingthe best mode thereof to one of ordinary skill in the art is set forthmore particularly in the remainder of the specification, includingreference to the accompanying figures, in which:

FIG. 1 illustrates a perspective top view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 2A illustrates a side view of an embodiment of an LED package witha heat transfer material according to FIG. 1;

FIG. 2B illustrates a side view of an embodiment of a mounted LEDpackage according to the subject matter herein;

FIG. 2C illustrates a side view of an embodiment of a mounted LEDpackage according to the subject matter herein;

FIG. 2D illustrates a side view of an embodiment of a mounted LEDpackage according to the subject matter herein;

FIG. 3A illustrates a perspective bottom view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 3B illustrates a perspective bottom view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 4 illustrates a perspective top view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 5A illustrates a side view of an embodiment of an LED package witha heat transfer material according to FIG. 4;

FIG. 5B illustrates a side view of an embodiment of a mounted LEDpackage according to the subject matter herein;

FIG. 5C illustrates a side view of an embodiment of a mounted LEDpackage according to the subject matter herein;

FIG. 5D illustrates a side view of an embodiment of a mounted LEDpackage according to the subject matter herein;

FIG. 5E illustrates a side view of an embodiment of an LED packageaccording to the subject matter herein;

FIG. 6A illustrates a perspective bottom view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 6B illustrates a perspective bottom view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 6C illustrates a perspective bottom view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 7 illustrates a perspective top view of an embodiment of an LEDpackage with a heat transfer material according to the subject matterherein;

FIG. 8 illustrates a perspective bottom view of an embodiment of an LEDpackage with a heat transfer material according to FIG. 7;

FIG. 9A illustrates a side view of an embodiment of an LED package witha heat transfer material according to FIG. 7;

FIG. 9B illustrates a side view of an embodiment of a mounted LEDpackage according to the subject matter herein;

FIG. 10A illustrates a side view of an embodiment of an LED package witha heat transfer material according to the subject matter herein;

FIG. 10B illustrates a top perspective view of an embodiment of an LEDpackage according to FIG. 10A;

FIG. 10C illustrates a bottom perspective view of an embodiment of anLED package according to FIG. 10A; and

FIG. 10D-10F illustrate bottom perspective views of embodiments of anLED package with grooves according to the subject matter herein.

DETAILED DESCRIPTION

Reference will now be made in detail to possible embodiments of thesubject matter herein, one or more examples of which are shown in thefigures. Each example is provided to explain the subject matter and notas a limitation. In fact, features illustrated or described as part ofone embodiment can be used in another embodiment to yield still afurther embodiment. It is intended that the subject matter disclosed andenvisioned herein covers such modifications and variations.

As illustrated in the various figures, some sizes of structures orportions are exaggerated relative to other structures or portions forillustrative purposes and, thus, are provided to illustrate the generalstructures of the present subject matter. Furthermore, various aspectsof the present subject matter are described with reference to astructure or a portion being formed on other structures, portions, orboth. As will be appreciated by those of skill in the art, references toa structure being formed “on” or “above” another structure or portioncontemplates that additional structure, portion, or both may intervene.References to a structure or a portion being formed “on” anotherstructure or portion without an intervening structure or portion aredescribed herein as being formed “directly on” the structure or portion.Similarly, it will be understood that when an element is referred to asbeing “connected”, “attached”, or “coupled” to another element, it canbe directly connected, attached, or coupled to the other element, orintervening elements may be present. In contrast, when an element isreferred to as being “directly connected”, “directly attached”, or“directly coupled” to another element, no intervening elements arepresent.

Furthermore, relative terms such as “on”, “above”, “upper”, “top”,“lower”, or “bottom” are used herein to describe one structure's orportion's relationship to another structure or portion as illustrated inthe figures. It will be understood that relative terms such as “on”,“above”, “upper”, “top”, “lower” or “bottom” are intended to encompassdifferent orientations of the device in addition to the orientationdepicted in the figures. For example, if the device in the figures isturned over, structure or portion described as “above” other structuresor portions would now be oriented “below” the other structures orportions. Likewise, if devices in the figures are rotated along an axis,structure or portion described as “above”, other structures or portionswould now be oriented “next to” or “left of” the other structures orportions. Like numbers refer to like elements throughout.

Light emitting devices according to embodiments described herein maycomprise III-V nitride (e.g., gallium nitride) based light emittingdiodes (LEDs) or lasers fabricated on a silicon carbide substrate, suchas those devices manufactured and sold by Cree, Inc. of Durham, N.C.Such LEDs and/or lasers may also be configured to operate such thatlight emission occurs through the substrate in a so-called “flip chip”orientation or by conventional wirebonding techniques.

Referring now to FIGS. 1-10F, FIG. 1 illustrates a top perspective viewof one embodiment of a light emitting device package, for example an LEDpackage, generally designated 10. Corresponding side and bottomperspective views of LED package 10 are illustrated in FIGS. 2A-2C and3A-3B. FIGS. 2B-2C illustrate LED package 10 engaging an external sourceor substrate, for example a printed circuit board (PCB) 30. LED package10 can comprise a body 18 housing one or more LED chips 12 a attached toan upper surface of a thermal element. An electrostatic discharge (ESD)protection device 12 b can be part of the LED package 10 and mounted toa top surface of an electrical element, for example a metal lead 20 a.For example, ESD protection device 12 b can comprise a Zener diode,ceramic capacitor, transient voltage suppression (TVS) diode, multilayervaristor, a Shottky diode and/or any other ESD device known in the art.

Body 18 can comprise a body selected from a group of materialsconsisting of molded plastic, polymeric, thermoset plastic,thermoplastic, ceramic, nylon, liquid crystal polymer (LCP), orpolyvinyl chloride (PVC) wherein body 18 can be disposed around thermaland electrical elements. The thermal element can comprise a heattransfer material or substrate 14, such as for example a heat slugdisposed on a bottom floor of a reflector cavity 16 of the package body18, and reflector cavity 16 can be coated with an encapsulant E.Encapsulant E can comprise any suitable material known in the art andcan optionally comprise a phosphor or a lumiphor to interact with lightemitted by the LED chips 12 a and responsively emit light of a differentwavelength spectrum. For illustration purposes, encapsulant E is shownto fill reflector cavity 16 essentially flush with an upper surface ofthe body. Encapsulant E however, may be filled to any suitable levelwithin the reflector cavity 16 or even exceed and extend above reflectorcavity 16 as known in the art.

The thermal element can comprise a thermal heat transfer material 14,and can comprise a metal or any other suitable thermally conductingmaterial known in the art. Heat transfer material 14 can be formedintegrally as one piece or, as illustrated in FIGS. 3A and 3B, maycomprise several portions, for example a protruding portion 14 aattached to and extending from a base portion 14 b of thermallyconducting material assembled together as known in the art. Heattransfer material 14 as well as all the other heat transfer materialsidentified and described further herein can be any suitable type of heattransfer device. In one aspect, heat transfer material 14 as well as allthe other heat transfer materials identified and described furtherherein can be an intermediary thermal structure for transferring heat toanother structure such as a heat transfer layer or a heat sink forfurther heat dissipation. In this aspect, heat transfer material 14 aswell as all the other heat transfer materials identified and describedfurther herein can be a thermal structure with limited heat capacity andcapable of heating up quite quickly if not effectively connectedthermally to a further heat transfer device such as an actual heat sink.

Wirebonding the LED chips 12 a and ESD device 12 b can electricallyconnect the LED chips 12 a and ESD device 12 b to electrical elements.Heat transfer material 14 can be electrically isolated from electricalelements 22 a and 22 b, for example isolated from metal leads 20 a and20 b, by insulating portions of body 18. An exposed lower surface 26 ofheat transfer material 14 can extend from a bottom surface 19 of body18. Heat transfer material 14 can conduct heat away from LED chips 12 aand LED package 10 allowing improved heat dissipation therefrom.

Electrical elements can comprise metal leads 20 a and 20 b formed from aleadframe which can serve as anode and cathode connections supplying theLED chips 12 a with current sufficient to cause light emission. Leads 20a and 20 b can comprise a metal or any other suitable electricallyconducting material known in the art. Vertical portions 25 a and 25 b ofleads 20 a and 20 b, respectively, can extend from body 18 at lateralexterior side walls of body 18. Vertical portions 25 a and 25 b canextend vertically in a downward direction from body 18 and can alsocomprise a portion orthogonal to linear portions 24 a and 24 b of leads20 a and 20 b. Linear portions 24 a and 24 b can extend outwards in alinear direction and in opposite directions away from the body 18 of theLED package 10. Vertical portions 25 a and 25 b can be located alongexterior sides disposed between an upper surface of the body 18 havingthe reflector cavity 16 and a bottom surface 19 of the body 18. Verticalportions 25 a and 25 b and linear portions 24 a and 24 b can eachcomprise a bend such as bend 27 disposed therebetween. That is, eachbend 27 provides a transitioning area wherein vertical portions 25 a and25 b transition perpendicularly into linear portions 24 a and 24 b,respectively. This arrangement of lead components can be referred to asa “gull wing” type lead component. Each bend 27 can be formed before ormore typically after formation of body 18 structure. Linear portions 24a and 24 b can be electrically connected to form an electrical contactswith an external source, such as for example, a PCB 30 as illustrated byFIGS. 2B and 2C. The gull wing type lead component can be difficult tomanufacture, as the body of the package is prone to damage when thepackage is subjected to bending forces required to induce the linearportions of the leads to bend out away from the body 18 and each other.

Referring now to FIG. 2B, linear portions 24 a and 24 b of leads 20 aand 20 b, as well as a bottom surface 26 of heat transfer material 14can be mounted to the PCB 30 using standard soldering techniques whereinsolder 32 wets bottom surfaces of both the thermal and electricalelements. Such techniques can comprise for example, soldering PCB 30 ina reflow oven or placing PCB 30 on a hotplate. Any suitable soldermaterial known in the art and capable of securing thermal and electricalelements, that is heat transfer material 14 and linear portions 24 a and24 b of leads 20 a and 20 b, to PCB 30 may be used. For example, asolder 32 can comprise a solder paste of gold, tin, silver, lead and/orcopper (Au, Sn, Ag, Pb, and/or Cu), reflow solder flux, and/or anycombination thereof. For example, Sn 96.5/Ag 3.0/Cu 0.5 is a commonPb-free solder as is Sn 95.5/Ag 3.8/Cu 0.7.

As further illustrated by FIGS. 2A-2D, heat transfer material, generallydesignated 14, can comprise bottom surface 26 which extends further awayfrom the body 18 at a greater distance than a distance from the body 18to bottom surfaces 28 a and 28 b of linear portions 24 a and 24 b,respectively, of leads 20 a and 20 b when package 10 is mounted, forexample by soldering, to the PCB 30. Thus, bottom surface 26 of heattransfer material 14 can be said to be extending a distance to a firstplane P1 which is lower than a second plane P2 which is the plane of thebottom surfaces 28 a and 28 b of linear portions 24 a and 24 b of leads20 a and 20 b. As shown by FIGS. 2A-2D, the bottom surfaces 28 a and 28b of the electrical element extend away from the body a first distance,and the bottom surface 26 of the thermal element extending away from thebody a second distance, and the second distance can be greater than thefirst distance. In one aspect, a suitable distance between P1 to P2 can,for example only and without limitation, be from slightly above 0 μm togreater than 100 μm. In other embodiments, the distance from P1 to P2can be from 25 μm to 50 μm, 50 μm to 100 μm, or greater than 100 μm.

As illustrated by FIG. 2B, once wetted by solder 32, any gap between thethermal element, that is, a gap 36 between bottom surface 26 of heattransfer material 14 and the PCB 30 will be smaller than a gap 34between the electrical elements, that is, the bottom surfaces 28 a and28 b of linear portions 24 a and 24 b of leads 20 a and 20 b and PCB 30.Having heat transfer material 14 in this configuration can increase thelikelihood that the solder 32 will wet the entire bottom surface 26 ofheat transfer material 14 and can allow formation of an adequate thermalcontact between the LED package 10 and PCB 30. Upon solidification ofthe solder 32, the thermal contact between heat transfer material 14 andPCB 30 can comprise a solder joint that is essentially free of voids,thereby being more reliable. This can increase the likelihood ofobtaining better heat transfer from heat transfer material 14 to PCB 30.For example, if LED package 10 were to be sheared from PCB 30, afootprint of the solder joint on the backside of the package and PCB 30would preferably be essentially free of voids. A small number, orsubstantially zero voids indicates better wetting of the thermalelement, and a better, more reliable thermal contact between heattransfer material 14 of LED package 10 and PCB 30. Bottom surface 26 ofheat transfer material 14 as well as bottom surfaces 28 a and 28 b ofportions of leads 24 a and 24 b are thus all wetted by solder 32 andconnected to the PCB 30 upon solidification of the solder 32.

Also illustrated by FIGS. 2B-2D, PCB 30 can be an intermediate substratelocated above a heat transfer layer 33 and a heat sink 35. Heat candissipate away from LED package 10 by moving in a path and pass from theheat transfer material 14 into solder 32 and then into the PCB 30. Heatcan then pass from PCB 30 and into heat transfer layer 33 which cancomprise any material known in the art that is thermally conductive.Heat continues on a path which passes from heat transfer layer 33 intoheat sink 35 which can pass heat into ambient air for example. Heat sink35 can comprise any material known in the art capable of conductingheat, and which ideally would not increase in temperature when heat isapplied.

FIGS. 2A-2D also illustrate bottom surface 26 of heat transfer material14 which can be disposed in a recess 38 that can be formed in or part ofthe bottom surface 19 of body 18. Recess 38 can allow the overflow ofsolder (such as solder 32) and/or flux to move into recess 38. Thisfeature can eliminate or reduce the need to clean residue left behind bythe attachment process, for example, using a “no-clean” solder. Recess38 can also allow more access for solvents to remove flux after thereflow process if using for example, a “clean” solder which must undergoa cleaning process. Because of process variability, the amount of solderand/or flux that is dispersed to connect components, such as heattransfer material 14 and PCB 30, can vary significantly. As the solderand/or flux can be very difficult to remove from substrates such asPCBs, recess 38 provides a space for any excess solder and/or flux toflow into thereby producing the area(s) needing cleaning afterwards.Exposed portions of heat transfer material 14 can be located withinrecess 38. For example, FIG. 2A shows exposed portions 1-3, 26, and 5-7of heat transfer material 14. Each exposed portion is an externalsurface of heat transfer material 14, which can be formed integrally asone piece, or formed from more than one portion such as protrudingportion 14 a and base portion 14 b illustrated in FIGS. 3A-3B. Asillustrated, at least one of the exposed portions 1-3, 26, and 5-7 ofheat transfer material 14 can be located above the bottom surface 28 aand 28 b of linear portions 24 a and 24 b of leads, that is locatedabove P2 while at least one of the exposed portions 1-3, 26, and 5-7 canbe located below P2.

More specifically, in high-temperature metal joining processes includingsoldering, flux can have a primary purpose of preventing oxidation ofthe base and filler materials. Flux is a substance which is nearly inertat room temperature, but which becomes strongly reducing at elevatedtemperatures, thus preventing the formation of metal oxides. Flux alsoacts as a wetting agent in the soldering process, reducing surfacetension of the molten solder and causing it to better wet the componentsbeing joined. Fluxes can comprise water-soluble fluxes so-called “clean”fluxes that do not require any volatile organic compounds for removaland “no-clean” fluxes which are mild enough to not require removal atall. Some fluxes are formulated to result in a residue which is notsignificantly corrosive, but cleaning is still preferred. As such, it isadvantageous that recess 38 provides a space for any excess solderand/or flux to flow into thereby producing the areas needing cleaningafterwards.

Referring to FIGS. 2C and 2D, PCB 30 can optionally comprise a notch 31that can extend either partially (FIG. 2C) or entirely through (FIG. 2D)PCB 30. Notch 31 can facilitate for example, the alignment of heattransfer material 14 or any other heat transfer materials when mountingto a thermally conductive element of an external substrate, such as aPCB 30. Other features correspond to FIGS. 2A and 2B described above. Atleast a portion of heat transfer material 14 can extend into and atleast partially or completely fill notch 31. That is, bottom surface 26of heat transfer material 14 can substantially correspond to a surfaceof notch 31 and sides of at least a portion of heat transfer material 14can be smaller than or substantially correspond in width to a width W ofnotch 31. Solder 32 can still flow around heat transfer material 14 toconnect heat transfer material 14 to PCB 30. Plane P1 of heat transfermaterial 14 can extend from P2 a distance required to fill notch 31. Forexample, the distance can be from slightly above 0 μm to 100 μm, from 25μm to 50 μm, or greater than 100 μm. As illustrated by FIG. 2D, notch 31can extend and comprise a depth entirely through PCB 30 wherein heattransfer material 14 can thermally contact and connect any suitablefurther heat dissipating structure or structures, such as heat transferlayer 33. This can further improve heat dissipation from the LED package10. For example, heat transfer material 14 can have at least a portionof bottom surface 26 soldered directly to heat transfer layer 33 whileat least a portion of exposed portions 1-3 and 5-7 (FIG. 2A) of heattransfer material 14 can be soldered to PCB 30. In FIGS. 2C and 2D, heatcan advantageously pass away from the LED package 10 and intointermediate components comprising heat transfer material 14, PCB 30,and heat transfer layer 33 before ultimately passing into heat sink 35.Alternatively, heat transfer material 14 can thermally contact andconnect with heat sink 35 directly without contacting an intermediatetransfer layer such as intermediate heat transfer layer 33.

Referring now to FIGS. 3A and 3B, these figures illustrate a perspectivebottom view of the features opposing the top view illustrated by FIG. 1.For example, heat transfer material 14 can be formed integrally as onepiece, or may be formed from several portions including protrudingportion 14 a and base portion 14 b. Base portion 14 b of the thermalelement extends from body 18. Protruding portion 14 a attaches to baseportion 14 b and can be dimensionally smaller on the sides than baseportion 14 b although it can be of a greater height or thickness thanbase portion 14 b as illustrated by FIG. 3B. Protruding portion 14 a andbase portion 14 b can comprise any size and/or shape known in the artand are not limited hereto. Having a protruding portion 14 a from a baseportion 14 b allows improved wetting as solder can more fully wet thesurface of protruding portion 14 a. Thus, a more uniform solder joint,or thermal connection, can form between the LED package 10 and PCB 30.Heat transfer material 14 can be disposed within recess 38 and linearportions 24 a and 24 b of electrical elements can be seen extendingoutwards from the body in a direction away from each other. FIG. 3Aillustrates a view wherein the distance between planes P1 and P2 can beas illustrated by FIG. 2A and can, for example only and withoutlimitation, range from slightly above 0 μm to 50 μm, 25 μm to 50 μm, or50 μm to 100 μm. FIG. 3B illustrates a larger heat transfer materialwherein the distance between planes P1 and P2 is greater and can begreater than 100 μm, and could be useful for applications as illustratedby FIGS. 2C and 2D. For applications utilizing distances greater thanabout 100 μm, notch 31 can be useful for alignment purposes and tofacilitate adequate contact between the thermal element, heat transfermaterial 14, and the PCB 30.

FIGS. 4-6C illustrate views of another embodiment of an LED package,generally designated as 40, having features which can correspondsubstantially in form and function to those of FIGS. 1-3B. For example,LED package 40 can comprise one or more LED chips 42 attached to anupper surface of a thermal element. One or more ESD devices (not shown)may be attached to an upper surface of an electrical element as well.Thermal element can comprise a heat transfer material generallydesignated 44 made of a thermally conducting material and disposed on abottom floor of a reflector cavity 46 of a package body 48. Aspreviously described, body 48 can comprise any suitable material knownin the art, and can be formed about, thereby encasing thermal andelectrical elements. Reflector cavity 46 can be coated with encapsulantE which can optionally containing a phosphor or lumiphor. Forillustration purposes encapsulant E is shown as substantially flush withan upper surface of the body 48 and the top of the reflector cavity 46,but it may be filled to any level above or below the top of thereflector cavity 46.

LED chips 42 can electrically connect to electrical elements, forexample metal leads 50 a and 50 b formed from a leadframe which serve asanode and cathode components supplying current to the LED chips 42. Heattransfer material 44 can be electrically isolated from leads 50 a and 50b by insulating portions 52 a and 52 b of the body 48. Heat transfermaterial 44 can conduct heat away from the LED chips 42 and allow heatto dissipate therefrom. Portions 55 of leads 50 a and 50 b can extendfrom the body 48 at a lateral exterior face and transition into linearportions 54 a and 54 b which can turn in towards each other and face thethermal element when mounted to an external source, for example a PCB60. Extending portions 55 of leads 50 a and 50 b can extend from thelateral exterior faces of body 48 and can comprise a first bend.Extending portions 55 can bend to form vertical portions 57 a and 57 bof leads 50 a and 50 b which can be orthogonal to linear portions 54 aand 54 b, respectively. Second bending portions 53 can be located alonga central axis beneath extending portions 55 and can perpendicularlytransition the vertical portions 57 a and 57 b into the linear portions54 a and 54 b, respectively, of leads 50 a and 50 b. This configurationcan be referred to as a “J-bend” type lead component. Linear portions 54a and 54 b form electrical contacts with the PCB 60 upon soldering.Linear portions 54 a and 54 b can electrically connect to the PCB 60using standard soldering processes as previously described. As with thegull wing type lead component, the J-bend type lead component can bedifficult to manufacture, as the body of the package is prone to damagewhen the package is subjected to bending forces required to induce thelinear portions of the leads to bend in to face each other.

As illustrated in FIGS. 5A-5E, heat transfer material 44 can comprise anexposed, bottom surface 56 which can extend a greater distance away frombody 48 of LED package than a distance from body 48 to bottom surfaces58 a and 58 b of linear portions of leads 54 a and 54 b, respectively,when package 40 is mounted, for example by soldering, to the PCB 60.Thus, bottom surface 56 of heat transfer material 44 extends to a lowerplane P1 than a plane P2 of which bottom surfaces 58 a and 58 b canextend to. As shown by FIGS. 5A-5E, the bottom surfaces 58 a and 58 b ofthe electrical element extend away from the body a first distance, andthe bottom surface 56 of the thermal element can extend away from thebody to a second distance. The second distance can be greater than thefirst distance. A gap 66, which can exist or form between bottom surface56 of heat transfer material 44 and PCB 60, can be smaller than a gap 64between the bottom surfaces 58 a and 58 b of leads 54 a and 54 b and PCB60. At least one of exposed portions 1-3, 56, and 5-7 of heat transfermaterial 44 can be located above the bottom surfaces 58 a and 58 b ofthe linear portions 54 a and 54 b, respectively, of the leads, locatedabove P2. Additionally, at least one of exposed portions 1-3, 56, and5-7 of heat transfer material 44 can be located below the bottomsurfaces 58 a and 58 b of the linear portions 54 a and 54 b,respectively, of the leads, located below P2. As described earlier,having heat transfer material 44 in this configuration can increase thelikelihood that the entire surface 56 of heat transfer material 44 willbe wetted by solder 62, which can allow formation of a good thermalcontact between heat transfer material 44 and PCB 60. This configurationcan allow LED package 40 to adapt to process variably in the amount ofsolder dispersed. Once the solder 62 solidifies, the thermal contact cancomprise a solder joint that is more reliable because it can be a jointessentially free of voids between LED package 40 and PCB 60. This canensure improved heat transfer from the bottom surface 56 of heattransfer material 44 to the PCB 60. In addition to bottom surface 56 ofheat transfer material 44, bottom surfaces 58 a and 58 b of linearportions 54 a and 54 b of the leads can be wetted by solder 62 to formelectrical contacts with PCB 60 once solder 62 solidifies.

Also illustrated by FIGS. 5B-5D, PCB 60 can comprise an intermediatesubstrate disposed above a heat transfer layer 63 and a heat sink 65.Heat can dissipate away from the LED package 40 by moving in a path andpass from heat transfer material 44 into solder 62 and then into PCB 60.Heat can then pass from PCB 60 and into heat transfer layer 63 which cancomprise any material known in the art that is thermally conductive.Heat continues on a path which passes from heat transfer layer 63 intoheat sink 65 which can pass heat into ambient air for example. Heat sink65 can comprise any material known in the art capable of conductingheat, and which ideally would not increase in temperature when heat isapplied.

Referring to FIGS. 5C-5D, PCB 60 can comprise a notch 61 That can extendeither partially (FIG. 5C) or entirely (FIG. 5D) through notch 61. Notch61 can facilitate for example, the alignment of heat transfer material14 or any other heat transfer materials when mounting to an externalsubstrate, such as a PCB 60. Other features correspond to FIGS. 5A and5B described earlier. Heat transfer material 44 can be formed integrallyin one piece or can comprise more than one portions, for example aprotruding portion 44 a and a base portion 44 b. At least a portion ofheat transfer material 44 can extend into notch 61. That is, bottomsurface 56 of heat transfer material 44 can substantially correspond tosurface of notch 61 and sides of at least a portion of heat transfermaterial 14 can substantially correspond in width to a width W of notch61. Solder 62 can still flow around heat transfer material 44 to connectheat transfer material 44 to PCB 60. Plane P1 of heat transfer material44 can extend from P2 a distance required to substantially engage notch61, which can, for example and without limitation, be greater than 100μm. For applications utilizing distances greater than about 100 μm,notch 61 can be useful for alignment purposes and to facilitate adequatecontact between the thermal element, heat transfer material 44, and thePCB 60.

Referring to FIG. 5D, notch 61 can extend and comprise a depth entirelythrough PCB 60 wherein heat transfer material 44 can be connecteddirectly with heat transfer layer 63. This can further improve heatdissipation from the LED package 40. For example, heat transfer material44 can have bottom surface 56 soldered directly to heat transfer layer63 while at least a portion of exposed portions 1-3 and 5-7 (FIG. 5A) ofheat transfer material 44 can be soldered to PCB 60. In FIGS. 5C and 5D,heat can advantageously pass away from LED package 40 and intointermediate components such as heat transfer material 44, PCB 60, andheat transfer layer 63 before ultimately passing into heat sink 65.Alternatively, heat transfer material 44 can thermally contact andconnect with heat sink 65 directly without contacting an intermediatetransfer layer such as intermediate heat transfer layer 63.

FIG. 5E illustrates bottom surface 56 of heat transfer material 44 whichcan be disposed in a recess 59 that can be formed in or part of thebottom surface 49 of body 48. Recess 59 can allow the overflow of solder(such as solder 62 in FIGS. 5B and 5C) and/or flux to move into recess59. This feature can eliminate or reduce the need to clean residue leftbehind by the attachment process. Because of process variability, theamount of solder and/or flux that is dispersed to connect components,such as heat transfer material 44 and PCB 60, can vary significantly. Asthe solder and/or flux can be very difficult to remove from substratessuch as PCBs, recess 59 provides a space for any excess solder and/orflux to flow into thereby producing the area(s) needing cleaningafterwards. Exposed portions of heat transfer material 44 can be locatedwithin recess 59. For example, FIG. 5A shows exposed portions 1-3, 56,and 5-7 of heat transfer material 44. Each exposed portion is anexternal surface of heat transfer material 44, which can be formedintegrally as one piece, or formed from more than one portion such asprotruding portion 44 a and base portion 44 b illustrated in FIGS.6A-6C. As illustrated, at least one of the exposed portions 1-3, 56, and5-7 of heat transfer material 44 can be located above the bottom surface58 a and 58 b of linear portions 54 a and 54 b of leads, that is locatedabove P2 while at least one of the exposed portions 1-3, 56, and 5-7 canbe located below P2.

Referring now to FIGS. 6A-6C, these figures illustrate a perspectivebottom view of the features opposing the top view illustrated by FIG. 4.For example, heat transfer material 44 can be formed integrally or byassembling one or more portions together, for example protruding portion44 a and base portion 44 b. Linear portions 54 a and 54 b of electricalelements can be seen as extending in towards the body and towards heattransfer material 44 to face each other. Base portion 44 b of thethermal element extends from the body 48. Protruding portion 44 aattaches to base portion 44 b and can be dimensionally smaller on thesides than base portion 44 b although it can be of a greater height orthickness than base portion 44 b as illustrated by FIG. 6B. Protrudingportion 44 a and base portion 44 b can comprise any size and/or shapeknown in the art and are not limited hereto. By having a protrudingportion 44 a from a base portion 44 b, improved wetting can be achievedas solder can more fully wet the surface of the protruding portion 44 a.Thus, a more uniform solder joint, or thermal connection, can formbetween the LED package 40 and PCB 60. FIG. 6A further illustrates aview wherein the distances between planes P1 and P2 (seen in FIG. 5A) ismore likely a range between 1 and 50 μm. FIG. 6B illustrates a viewwherein the distances between planes P1 and P2 is greater, and morelikely greater than 100 μm, and could be useful for applications asillustrated by FIGS. 5C and 5D. FIG. 6C illustrates a view wherein arecess 59 can be formed in or part of the bottom surface 49 of body 48as seen in FIG. 5E.

FIGS. 7-9B illustrate top perspective, bottom perspective, and sideviews of another embodiment of an LED package, generally designated 70,which has features that can substantially correspond in form andfunction to the embodiments shown by FIGS. 1-6C. For example, LEDpackage 70 can comprise one or more LEDs 100 a attached to an uppersurface of a thermal element and electrically connected to at least oneelectrical element. One or more ESD devices 100 b can also be attachedto an upper surface of an electrical element. The thermal element cancomprise a heat transfer material 72, and the electrical elements cancomprise metal leads 74 a and 74 b of a leadframe. The thermal andelectrical elements can be contained within a molded plastic body 76having a reflector cavity 76 a and can comprise a thickness from anupper surface comprising the LEDs 100 a to a bottom surface 76 b of theLED package 70. A suitable amount of optically transmitting encapsulantE can fill the reflector cavity to a suitable level within the reflectorcavity 76 a. Heat transfer material 72 can be electrically isolated frommetal leads 74 a and 74 b by insulating portions 70 a and 70 b of body76. Heat transfer material 72 and leads 74 a and 74 b can extend to atleast one exterior lateral side 79 a of body 76 wherein the material issheared resulting in exposed portions which can be flush with theexterior lateral side 79 a. For example, heat transfer material 72 canbe sheared on the exterior lateral side 79 a of body 76 to leave exposedportion 73 flush with the surface of lateral side 79 a. Similarly, metalleads 74 a and 74 b can be sheared flush with the surface of the lateralside 79 a, resulting in exposed portions 71 a and 71 b, respectively, onlateral side 79 a. Retention notches 75 can be located on at least asecond exterior lateral side 79 b of body 76 adjacent first lateral side79 a having the sheared, exposed portions 73, 71 a, and 71 b. Retentionnotches 75 can improve handling of LED package 70 during processing.

FIG. 8 illustrates the bottom perspective view of the featuresillustrated by FIG. 7. In this embodiment, leads 74 a and 74 b extendfrom bottom surface 76 b which is substantially orthogonal to exteriorlateral sides 79 a and 79 b of the LED package 70. That is, leads 74 aand 74 b do not comprise portions which extend beyond any lateralexterior side or any lateral exterior surface of LED package 70. Asillustrated in FIGS. 9A and 9B, heat transfer material 72 can comprise abottom surface 78 which can extend to a greater distance away from body76 of LED package 70 than a distance from body 76 to bottom surfaces 80a and 80 b of leads 74 a and 74 b, respectively, when package 70 ismounted to a PCB 90. That is, heat transfer material 72 can extend tohave its bottom surface 78 located on a plane P1 which is lower than aplane P2 of the bottom surfaces 80 a and 80 b of leads 74 a and 74 b,respectively. In one embodiment, a suitable range in distance between P1and P2 can be from slightly above 0 μm to greater than 100 μm. In otherembodiments, a suitable range in distance between P1 and P2 can be fromabout 25 μm to 50 μm, 50 μm to 100 μm, or greater than 100 μm. Whenpackage 70 is mounted, for example by soldering, to a PCB 90, a gap 96can exist between the bottom surface 78 of heat transfer material 72 andPCB 90 which can be smaller than a gap 94 existing between bottomsurfaces 80 a and 80 b of leads 74 a and 74 b and the PCB 90. A moreuniform and reliable thermal contact, or solder joint created betweenheat transfer material 72 and PCB 90, can form once solder 92 solidifiessuch that the thermal contact is essentially free of voids. As such,overall heat transfer, heat dissipation capability, and thermalproperties of LED package 70 are improved. In addition to bottom surface78, bottom surfaces 80 a and 80 b of leads 74 a and 74 b can also bewetted by solder 92 to form electrical contacts with PCB 90.

Also illustrated by FIG. 9B, PCB 90 can comprise an intermediatesubstrate disposed above a heat transfer layer 93 and a heat sink 95.Heat can dissipate away from LED package 70 by moving in a path and passfrom heat transfer material 72 into solder 92 and then into PCB 90. Heatcan then pass from PCB 90 and into heat transfer layer 93 which cancomprise any material that is thermally conductive. Heat can continue ona path which passes from heat transfer layer 93 into heat sink 95 whichcan pass heat into ambient air for example. Heat sink 95 can compriseany material capable of conducting heat, and which ideally would notincrease in temperature when heat is applied.

FIGS. 10A-10F illustrate side, top perspective, and bottom perspectiveviews of a further embodiment of a light emitting diode package 120.This embodiment illustrates using another LED packaging technologyutilizing methods such as low temperature co-fired ceramic (LTCC)instead of molding about lead portions from a leadframe. For example,the body can comprise an insulating member, such as a submount 122. Anactive layer 118 can be disposed on a top surface of the submount 122.Active layer 118 can comprise a light emitting device connected toelectrical components. For example, light emitting device can comprisean LED chip 110 electrically connected to electrical componentscomprising an anode 114 and a cathode 112. Anode 114 and cathode 112 cancomprise a metal or any other suitable electrically conductive materialknown in the art. LED chip 110 can optionally be coated with a phosphorfor producing a desired light wavelength spectrum. Active layer 118 canbe electrically and thermally connected to the body, or submount 122.Submount 122 can comprise one of many different materials includingthose which are electrically insulating. Suitable materials can comprisefor example, ceramic materials including aluminum oxide, aluminumnitride, or organic insulating materials such as polyimide (PI) andpolyphthalamide (PPA).

An optical element or lens 116 can be disposed over the top surface ofthe submount 122 and enclose LED 110 and at least a portion of activelayer 118. Lens 116 can comprise a molded lens of any suitable size andshape for producing a desired light output. Anode 114 and cathode 112can electrically couple to electrical elements of the LED package 120.Electrical elements can comprise first and second surface pads 124 and128, to which anode 114 and cathode 112 can electrically connect,respectively. First and second surface pads 124 and 128 can be disposedor mounted on a bottom surface 130 of submount 122 or they can be flushwith bottom surface 130. LED package 120 can further comprise a thermalelement, for example a heat transfer material 126. Heat transfermaterial 126 can be disposed or mounted to bottom surface 130 ofsubmount 122. Heat can dissipate from active layer 118 by extendingthrough thermally conductive paths in submount 122. Heat transfermaterial 126 can comprise any thermally conductive material known in theart and can be disposed between the first and second surface pads 124and 128.

Heat transfer material 126 can be substantially centrally and verticallyaligned beneath LED chip 110. Heat transfer material 126 may not be inelectrical contact with active layer 118 or first and second pads 124and 128. Heat can pass into submount 122 directly below and around LEDchip 110. Heat transfer material 126 can comprise any size and shapesuitable to assist with the dissipation of heat by allowing the heat tospread where it can dissipate to an external source or substrate, forexample a PCB having, for example, a heat sink. A bottom surface 132 ofheat transfer material 126 can extend to a plane P1 which is furtheraway in distance from bottom surface 130 of submount 122 than bottomsurfaces of the electrical elements. For example, electrical elementscan comprise first and second pads 124 and 128 having bottom surfaces134 and 136 respectively. Bottom surfaces 134 and 136 can extend to aplane P2 that is closer in distance to bottom surface 130 of submount122 than P1 or flush with bottom surface 130. In one embodiment, asuitable range for a distance between P1 to P2 can be from 0 μm togreater than 100 μm. In other embodiments, a suitable range for adistance between P1 and P2 can be from 25 μm to 50 μm, 50 μm to 100 μm,or greater than 100 μm. As previously described, this configurationenables adequate wetting of bottom surface 132 of heat transfer material126 when soldered to a PCB. Improved heat dissipation and improvedthermal properties of LED package 120 are thereby accomplished.

As illustrated by FIG. 10A, LED package 120 can be mounted to anexternal source, such as a PCB 150. PCB 150 can be an intermediatesubstrate located above a heat transfer layer 152 and a heat sink 154.Solder 160 can be used to attach LED package 120 to PCB 150. Forexample, once wetted by solder 160, any gap between the thermal element,that is, a gap 158 between bottom surface 132 of heat transfer material126 and PCB 150 will be smaller than a gap 156 between the electricalelements, that is, the bottom surfaces 134 and 136 of respective firstand second surface pads 124 and 128 and PCB 30. Having heat transfermaterial 126 in this configuration can increase the likelihood thatsolder 160 will wet the entire bottom surface 132 of heat transfermaterial 126 and can allow formation of an adequate thermal contactbetween LED package 120 and PCB 150. Upon solidification of the solder160, the thermal contact between heat transfer material 126 and PCB 150can comprise a solder joint that is essentially free of voids, therebybeing more reliable. This can increase the likelihood of obtainingbetter heat transfer from heat transfer material 126 to PCB 150. Forexample, if LED package 120 were to be sheared from PCB 150, a footprintof the solder joint on the backside of the package and PCB 30 wouldpreferably be essentially free of voids. A small number, orsubstantially zero voids indicates better wetting of the thermalelement, and a better, more reliable thermal contact between heattransfer material 126 of LED package 120 and PCB 150. Bottom surface 132of heat transfer material 126 as well as bottom surfaces 134 and 135 ofportions of first and second surface pads 124 and 128, respectively arethus all wetted by solder 160 and connected to PCB 150 uponsolidification of solder 160.

Referring now to FIGS. 10D, 10E and 10F, bottom surface 132 of heattransfer material 126 can comprise grooves 140 which can further improveheat dissipation of LED package 120 by breaking up small voids which mayform when LED package 120 is attached to PCB 150 (FIG. 10A). Asillustrated by FIG. 10D, one or more grooves 140 can be defined inbottom surface 132 of heat transfer material 126 and extend in a lineardirection along a first length. Where a plurality of grooves 140 arepresent, they can extend parallel to one another. As illustrated by FIG.10E, grooves 140 can extend in a linear direction along a second lengthwhich can be in a direction orthogonal with the first length. Asillustrated by FIG. 10F, grooves 140 can extend in more than onedirection, such as for example as shown in FIG. 10F where grooves 140extend in two directions that can be orthogonal to one another forming aplurality of island structures that are surrounded on at least two ormore, and even all four, sides by grooves 140. Grooves such as grooves140 can extend in any suitable direction even other than the directionsshown in FIGS. 10D-10F. Additionally, the island structures that can beformed between the grooves can be any suitable configuration, such asfor example and without limitation, rectangular, square, circular posttype configuration, or any other suitable configuration.

Embodiments of the present disclosure shown in the drawings anddescribed above are exemplary of numerous embodiments that can be madewithin the scope of the appended claims. It is contemplated that theconfigurations of LED packages having improved solder reliability forheat transfer, and methods of making the same can comprise numerousconfigurations other than those specifically disclosed.

What is claimed is:
 1. A light emitting device package, the packagecomprising: a body comprising at least a portion of a thermal elementand at least a portion of an electrical element, the electrical elementcontained between lateral sides of the body without extending beyond thelateral sides of the body; at least one light emitting device mounted ona top surface of the body; and both the thermal element and theelectrical element extending from a bottom surface of the body wherein abottom surface of the electrical element extends away from the body afirst distance, and a bottom surface of the thermal element extends awayfrom the body a second distance that is greater than the first distance.2. The light emitting device package according to claim 1, furthercomprising a lens.
 3. The light emitting device package according toclaim 1, wherein the second distance is greater than the first distanceby from about 0 μm to about 100 μm.
 4. The light emitting device packageaccording to claim 1, wherein the second distance is greater than thefirst distance by greater than about 100 μm.
 5. The light emittingdevice package according to claim 1, wherein the body comprises aninsulating material.
 6. The light emitting device package of claim 1,wherein the electrical element extends to a first plane and the thermalelement extends to a second plane which is lower than the first plane.7. The light emitting device package of claim 1, wherein the bodycomprises a reflector cavity.
 8. A light emitting device package, thepackage comprising: a body comprising at least a portion of a thermalelement and at least a portion of an electrical element, the electricalelement and the thermal element both contained between lateral sides ofthe body without extending beyond the lateral sides of the body; atleast one light emitting device thermally connected with the thermalelement; and both the thermal element and the electrical elementextending from a bottom surface of the body wherein a bottom surface ofthe electrical element extends away from the body a first distance, anda bottom surface of the thermal element extends away from the body asecond distance that is greater than the first distance.
 9. The lightemitting device package according to claim 8, further comprising a lens.10. The light emitting device package according to claim 8, wherein thesecond distance is greater than the first distance by from about 0 μm toabout 100 μm.
 11. The light emitting device package according to claim8, wherein the second distance is greater than the first distance bygreater than about 100 μm.
 12. The light emitting device packageaccording to claim 8, wherein the body comprises an insulating material.13. The light emitting device package of claim 8, wherein the electricalelement extends to a first plane and the thermal element extends to asecond plane which is lower than the first plane.
 14. The light emittingdevice package of claim 8, wherein the body comprises a reflectorcavity.
 15. A light emitting device package, the package comprising: abody comprising a first surface and a second surface; at least one lightemitting device mounted on the first surface of the body; an electricalelement contained between lateral sides of the body without extendingbeyond the lateral sides of the body, wherein at least a portion of theelectrical element is exposed on the second surface of the body; theelectrical element having an electrical element bottom surface that isdisposed along a first plane; and a thermal element with a thermalelement bottom surface that is disposed along a second plane that isdifferent from the first plane.
 16. The light emitting device package ofclaim 15, wherein the portion of the electrical element exposed on thesecond surface is flush with the second surface.
 17. The light emittingdevice package of claim 15, wherein the portion of the electricalelement exposed on the second surface extends away from the secondsurface a distance that is less than a distance the thermal elementextends away from the second surface.
 18. A light emitting devicepackage, the package comprising: a body comprising a first surface and asecond surface; at least one light emitting device electricallyconnected to an anode and a cathode on the first surface of the body; atleast one electrical element on the second surface of the body that iselectrically connected to at least one of the anode and cathode; athermal element on the second surface of the body; and wherein the atleast one electrical element extends away from the second surface of thebody a first distance and the thermal element extends away from thesecond surface of the body a second distance that is greater than thefirst distance.